A stack structure type sensor device includes a sensor chip having a membrane mounted on a circuit chip with adhesion bond. The sensor chip includes a semiconductor substrate such as silicon substrate. One side of the substrate is etched so that a concavity is formed. Then, the membrane made of insulation film or the substrate itself is formed on the other side of the substrate so that the concavity of the substrate is covered with the membrane.
In a case where the sensor device is used for an acceleration sensor or an angular rate sensor, the membrane has a comb-teeth sensing portion for detecting electric capacitance. A clearance in the comb-teeth sensing portion provides a passage for passing the air from the concavity to the outside of the concavity. Therefore, even if the air in the concavity is thermally expanded, the air can be released through the passage.
However, in a case where the sensor device is used for an infrared sensor or a pressure sensor, the concavity of the substrate is sealed with the membrane air-tightly. Therefore, in case of manufacturing the device, a stress is applied to the membrane because of thermal expansion of the air in the concavity. Thus, the membrane may be broken by the stress.
A technique is disclosed in Japanese Patent Application Publication No. 2002-33341. A convexity portion is formed on one side of the circuit chip, on which the sensor chip is mounted. Thus, the sensor chip is mounted on the convexity portion so that a clearance for releasing the air is formed. The clearance is formed between the sensor chip and the circuit chip in a portion except for the convexity portion. However, it is difficult to manufacture the circuit chip having the convexity portion.
Further, the adhesion bond is a liquid type adhesion bond such as diebond paste. This technique is disclosed, for example, in Japanese Patent Application Publication No. H07-58134. When the sensor chip is mounted on the circuit chip with the adhesion bond, the adhesion bond may crawl up to the sensor chip. Therefore, the adhesion bond may stick to the membrane, so that performance of the sensor chip is reduced. Moreover, a movable portion of the membrane may be fixed so that the sensor device does not work. Thus, reliability of the stack type sensor device having the sensor chip is decreased.